/Engine/Plugins/Developer/Concert/ConcertMain/Source/ConcertServer/Public/IConcertServer.h
typedef TBaseDelegate_FourParams< bool, const [FGuid](API\Runtime\Core\Misc\FGuid) &, const [FGuid](API\Runtime\Core\Misc\FGuid) &, const [FConcertClientInfo](API\Plugins\Concert\FConcertClientInfo) &, [FText](API\Runtime\Core\Internationalization\FText) * > FOnConcertParticipantCanJoinSession